Notation declarations provide a name for the notation, for use in entity and attribute-list declarations and in attribute specifications, and an external identifier for the notation which may allow an XML processor or its client application to locate a helper application capable of processing data in the given notation.

as a Name, not a reference, appearing either as the value of an attribute which has been declared as type ENTITY, or as one of the space-separated tokens in the value of an attribute which has been declared as type ENTITIES.

As a consequence of this, for each non-root element C in the document, there is one other element P in the document such that C is in the content of P, but is not in the content of any other element that is in the content of P. P is referred to as the parent of C, and C as a child of P.

While they are not required to check the document for validity, they are REQUIRED to process all the declarations they read in the internal DTD subset and in any parameter entity that they read, up to the first reference to a parameter entity that they do not read; that is to say, they MUST use the information in those declarations to normalize attribute values, include the replacement text of internal entities, and supply default attribute values.

as a reference within either the internal or external subsets of the DTD, but outside of an EntityValue, AttValue, PI, Comment, SystemLiteral, PubidLiteral, or the contents of an ignored conditional section (see )..

For an internal entity, the replacement text is the content of the entity, after replacement of character references and parameter-entity references.

For an external entity, the replacement text is the content of the entity, after stripping the text declaration (leaving any surrounding white space) if there is one but without any replacement of character references or parameter-entity references.

The SystemLiteral is called the entity's system identifier. It is meant to be converted to a URI reference (as defined in , updated by ), as part of the process of dereferencing it to obtain input for the XML processor to construct the entity's replacement text.